Jon Haidt is a brilliant NYU Stern social psychologist who is relentless in his scientific pursuit of the truth. The "Anxious Generation" is a must-read for every parent, educator, administrator and politician, because it documents the enormous and quantifiable "negative externalities" spawned by social media usage. The trends documented are especially deleterious for teenage girls. Haidt marshals evidence of depression, anxiety, self-harm and even suicide and concludes: "Social media use does not just correlate with mental illness; it causes it."An apt analogy to smoking is drawn, given social media apps are - by design - addicting and marketed to minors. Modern societal norms don't allow pre-teens to buy tobacco, alcohol or enter casinos so why are we allowing them access to "digital fentanyl"? Unfortunately, in a world of "move fast and break things" techno-optimism, what has been broken is teenage mental health. Haidt correctly assesses that this is a collective action problem and offers four foundation recommendations:1) More unsupervised play and childhood independence;2) No smartphones before high school;3) No social media before 16;4) Phone free schools;Regulatory frameworks and societal norms often lag Silicon Valley's bleeding-edge speed of development, but the damage being wrought here - and painstakingly documented by Haidt - is becoming visible enough that this book could catalyze real, positive and lasting change. Gift a copy to anyone with younger children or local educators - spread the word and help solve the collective action problem.Final note: All of Haidt's books are highly recommended, it is just an unfortunate reflection on our current state of affairs that the arc of his publishing gamut runs chronologically from Happiness to Anxiety instead of the reverse order.